Weathering test method

ABSTRACT

A weathering test method comprising making active oxygen and light simultaneously act on a test piece, a weathering test method comprising successive and/or alternate steps of making active oxygen and light simultaneously act on a test piece and making at least one of light, oxygen, and water to act on the test piece, and apparatus for carrying out the methods are disclosed. In evaluating weatherability of organic materials, articles made of organic materials or articles coated with organic materials, the methods and apparatus achieve acceleration of deterioration of test pieces to greatly reduce the testing time.

FIELD OF THE INVENTION

[0001] This invention relates to a test method for evaluatingweatherability of articles and materials thereof and an apparatus forcarrying out the test. More specifically, the invention is applied to aweatherability test of organic materials, articles made of the organicmaterials, articles coated with the organic materials, and the likewhich are used outdoors.

BACKGROUND OF THE INVENTION

[0002] Weathering tests designed to evaluate weatherability of organicmaterials such as coatings include an outdoor exposure test in which atest piece is exposed to the weather and a traced and collected sunlightexposure test in which a test piece is exposed to traced and collectedsunlight. In addition, special test methods include an artificialaccelerated weathering test in which a test piece is irradiated withlight from an artificial light source by means of a weatheringapparatus, such as a sunshine weather meter, a UV carbon weatherometer,a xenon weatherometer, a dew panel weatherometer, and a metal halideweatherometer.

[0003] JP-A-48-60695 discloses a method for accelerating a salt spraytest for evaluating anticorrosion of steel stock against seawater, inwhich hydrogen peroxide-added salt water is used as testing seawater.

[0004] The above-mentioned outdoor exposure test and traced andcollected sunlight exposure test require an extremely long period oftime not shorter than several months for test pieces to be deteriorated.It has been impossible with these weathering tests to evaluateweatherability rapidly.

[0005] The problem of the artificial accelerated weathering test, on theother hand, is that the test fails to sufficiently reproduce thedeterioration that should have been resulted from exposure to naturalweathering conditions. That is, the deteriorated state of a test piecedoes not agree with that in the outdoors for the following reason. Whenarticles or materials are long-term exposed outdoors, their deterioratedsurface, typically the coating film, shows a surface profile with finewaviness and fine pits in a mixed state, both of which reduce thesurface gloss, whereas the surface profile developed in the acceleratedweathering test mainly displays fine waviness so that the reduction ingloss as observed is chiefly ascribed to the fine waviness alone.

[0006] The above-described improved salt spray test aims at accelerationof a durability test, but its application is limited to evaluation ofanticorrosion of steel stock against seawater in special fields. It doesnot apply to weatherability testing of organic materials or articlesthereof.

SUMMARY OF THE INVENTION

[0007] An object of the present invention is to provide a test methodand an apparatus for evaluating weatherability of organic materials,articles made of organic materials, and materials coated with organicmaterials in an accelerated manner to greatly reduce the testing time.

[0008] Another object of the invention is to provide a weathering testmethod and an apparatus therefor which greatly speed up deterioration ofa test piece while achieving satisfactory reproduction of outdoordeterioration.

[0009] The invention relates to a weathering test method and aweathering apparatus for evaluating weatherability of a test piece suchas an organic material, an article made of an organic material or anarticle coated with an organic material.

[0010] The invention provides in its first aspect a weathering testmethod comprising making active oxygen and light simultaneously act on atest piece and evaluating the resultant deterioration, and a weatheringapparatus used to carry out the test method.

[0011] The invention provides in its second aspect a weathering testmethod comprising successive and/or alternate steps of making activeoxygen and light simultaneously act on a test piece and making at leastone of light, oxygen, and water to act on the test piece, and aweathering apparatus used to carry out the test method.

BRIEF DESCRIPTION OF THE INVENTION

[0012]FIG. 1 is a graph showing the relationship between light exposuretime and 60° gloss in Example 2.

[0013]FIG. 2 shows the relationship between light exposure time and 60°gloss in Example 3.

[0014]FIG. 3 displays the relationship between testing time and 60°gloss in Example 4.

[0015]FIG. 4 depicts the relationship between testing time and 60° glossin Comparative Example 3.

[0016]FIG. 5 shows the relationship between outdoor exposure time and60° gloss in Comparative Example 4.

[0017]FIG. 6 is a schematic illustration of a weathering apparatusaccording to the invention.

[0018]FIG. 7 schematically illustrates another weathering apparatusaccording to the invention.

[0019]FIG. 8 is a graph of warm water immersion time and light exposuretime vs. 60° gloss in Example 7.

[0020]FIG. 9 is an illustration showing the cycle of treatments inExample 8 and the apparatus therefor.

[0021]FIG. 10 depicts the relationship between 60° gloss and the numberof test cycles in Example 8.

[0022]FIG. 11 shows the relationship between testing time and 60° glossin Example 9.

[0023]FIG. 12 displays the relationship between testing time and 60°gloss in Comparative Example 8.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The weathering test according to the first aspect of theinvention is characterized in that active oxygen is made to act on atest piece simultaneously with irradiation.

[0025] Deterioration of materials is in general a phenomenon that thematerial absorbs light energy to become an active species, which reactswith oxygen in the atmosphere to undergo chemical denaturation.According to the invention, the above-mentioned chemical reaction isaccelerated by making light and active oxygen simultaneously act on atest piece to markedly speed up the deterioration phenomenon of the testpiece and thereby greatly shortening the time required for testing.

[0026] In the practice of the weathering test according to the firstaspect of the invention, active oxygen can be made to act on a testpiece either directly or indirectly. The case where active oxygen ismade to act on the test piece indirectly is preferred to the case whereactive oxygen is made to act on the test piece directly.

[0027] For example, in a preferred embodiment, active oxygen is allowedto directly act on a test piece by bringing active oxygen into directcontact with a test piece. This can be achieved by subjecting a testpiece to an oxygen plasma treatment.

[0028] Considering that active oxygen is difficult to handle in storingor weighing because of its high reactivity, it is another preferredembodiment that active oxygen is allowed to act indirectly on a testpiece by bringing a substance capable of releasing active oxygen(hereinafter referred to as an active oxygen-releasing substance) intocontact with a test piece. The active oxygen-releasing substanceincludes oxidizing agents containing oxygen. Oxidizing agents containingoxygen include hydrogen peroxide, ozone, peracids, peracid salts,hypohalogenous acids, and hypohalogenous acid salts. Hydrogen peroxideis preferred. The contact between the test piece and the activeoxygen-releasing substance may be either directly or indirectly. Thedirect contact can be made by, for example, coating the test piece witha liquid active oxygen-releasing substance.

[0029] However, where the oxygen-releasing substance is brought intodirect contact with a test piece, it is difficult to control the actionof released active oxygen on the test piece, which will limit theapplicability of the test method. Therefore, it is still anotherpreferred embodiment that the active oxygen-releasing substance isbrought into indirect contact with a test piece by using a water-solubleactive oxygen-releasing substance in the form of its aqueous solution.Of the above-described active oxygen-releasing substances, water-solubleones include hydrogen peroxide and hypohalogenous acid salts. An aqueoussolution of hydrogen peroxide (hereinafter referred to as aqueoushydrogen peroxide) is particularly preferred. In this preferredembodiment using the active oxygen-releasing substance in aqueoussolution, deterioration is accelerated easily, and the concentration ofthe oxidizing agent is easily controllable, making it easy to controlthe speed of deterioration.

[0030] The contact of the aqueous solution of the activeoxygen-releasing substance is preferably achieved by (i) immersing thetest piece in the aqueous solution or (ii) dropping or spraying theaqueous solution onto the test piece.

[0031] It is also still another preferred embodiment that the activeoxygen-releasing substance is brought into indirect contact with a testpiece by (iii) penetrating the active oxygen-releasing substance intothe test piece and letting the substance release active oxygen insidethe test piece. In this case, too, hydrogen peroxide is preferably usedas an active oxygen-releasing substance.

[0032] The water-soluble active oxygen-releasing substance includeshydrogen peroxide and hypohalogenous acid salts. Hydrogen peroxide isparticularly preferred for its high reactivity, i.e., high capability ofaccelerating deterioration. In using hydrogen peroxide in aqueoussolution, an effective concentration ranges from 0.001 to 60% by weight,preferably from 0.01 to 10% by weight. In concentrations lower than0.001%, the degree of deterioration acceleration tends to beinsubstantial for achieving the effects as expected in the invention.Concentrations exceeding 60% tend to cause deterioration too rapidly tostop the deterioration reaction under proper treating conditions, whichwill impair the accuracy of the test. With the concentration fallingwithin the preferred range of from 0.01 to 10%, reproducibility of thetest can be secured, and the test can be accomplished in a short timewith improved accuracy.

[0033] Where hydrogen peroxide is used in the form of an aqueoussolution which is brought into contact with a test piece or wherehydrogen peroxide is penetrated into a test piece, it is desirable thatthe test piece be kept at 0 to 120° C. At the test piece's temperaturelower than 0° C., the degree of deterioration acceleration tends to beinsufficient for manifesting the effects of the invention as expected.At the test piece's temperature higher than 120° C., cases are sometimesmet with, in which some chemical reaction that would not take placeoutdoors may occur, failing to achieve the object of the test.

[0034] According to the first aspect of the invention, a test piece isirradiated with light while receiving the action of active oxygen. Lightto be used is not particularly limited as long as it has energy toactivate the material making up the test piece. Because many ofindustrially important materials mutually react with light havingwavelengths not more than 400 nm, it is desirable for the irradiatinglight to contain light rays having wavelengths of 400 nm or less. Anylight source that has been employed in conventional weathering tests canbe adopted in the present invention. Suitable light includes not onlysunlight but light from artificial light sources, such as a xenon lamp,a metal halide lamp, a carbon arc lamp, and a UV fluorescent lamp, and acombination thereof. If necessary, an appropriate optical filter can beused in combination.

[0035] The weathering test according to the first aspect of theinvention is preferably carried out by means of a weathering apparatuscomprising a thermostat in which a test piece is put, a means for makingactive oxygen act on the test piece in the thermostat, and a means formaking light act on the test piece. Preferred examples of the apparatuswill be described in detail in Examples hereinafter given.

[0036] The language “making active oxygen and light simultaneously acton a test piece” as used herein means that irradiation may not benecessarily made to act on a test piece simultaneously with a treatmentusing an oxidizing agent, provided that light is made to act on the testpiece in the presence of the active oxygen.

[0037] The weathering test method according to the second aspect of theinvention comprises a first step of making active oxygen and lightsimultaneously act on a test piece and a second step of making at leastone of light, oxygen, and water to act on the test piece, the first andthe second steps being performed successively and/or alternately.

[0038] In general, outdoor deterioration of materials and articles madeof the materials (hereinafter inclusively referred to as material (s))is a phenomenon that the material undergoes chemical denaturation by theactions of water, oxygen and light in the environment. Of these actions,the action of water is to cause hydrolysis to degrade part of thematerial to low-molecular substances and to remove the low-molecularsubstances from the surface through extraction and vaporization. As aresult, fine waviness develops on the surface of the material. When thishappens on, for example, a resin-coated article, the resin except forpigments shrinks, and fine waviness of the surface results to reduce thesurface gloss.

[0039] The action of light is to give light energy to the material tomake it an active species, which reacts with oxygen in the atmosphere toform and/or sever various chemical bonds. By this action of light, partof the material is denatured into low-molecular substances, which areextracted and vaporized from the surface to develop fine waviness on thesurface.

[0040] Further, in the case of coating materials comprising resins andpigments and articles coated therewith, some pigments havephotocatalysis to accelerate local deterioration around the pigmentparticles. One of the characteristics of the surface profile observed inthis case is that the resin around the pigment particles in thevicinities of the surface is lost to leave fine pits on the surface.These pits as well as the fine waviness reduce the gloss of the coatingfilm.

[0041] In fact, close examination of the surface profile of a coatingfilm having deteriorated by outdoor exposure usually reveals finewaviness and fine pits in a mixed state. This indicates that theweathering action produces both fine waviness and fine pits. Therefore,in order to reproduce weathering deterioration in an accelerated manner,it is necessary to accelerate at least one of the actions of water andof light causing fine waviness and also the action of light causing finepits. From this viewpoint, the conventional accelerated weathering testsfail to reproduce outdoor deterioration and are inadequate as a testaiming at reproduction of outdoor deterioration.

[0042] In this regard, the weathering test according to the secondaspect of the invention achieves acceleration and reproduction of theoutdoor deterioration that could not be reproduced in the conventionalaccelerated weathering tests while properly balancing theabove-mentioned various actions. That is, the weathering test is toreproduce the surface profile of the material, for example, a coatingfilm having deteriorated by outdoor exposure.

[0043] In detail, the first step is to accelerate deterioration bymaking both active oxygen and light to act on a test piece to developfine pits as observed in outdoor deterioration. For example, somepigments contained in the resin coating film exert photocatalysis toinduce an oxidation reaction around the pigment particles as mentionedabove. It follows that the resin is lost to leave fine pits in anaccelerated manner. In the second step, on the other hand, fine wavinessdevelops on the surface of the test piece thereby achieving accelerateddeterioration. Specifically, where water is made to act, the coatingfilm, etc. are partially hydrolyzed with water and degraded intolow-molecular substances, which are lost through extraction orvaporization. It follows that the coating film, etc. shrink to developfine waviness on the surface thereby to accelerate deterioration. Wherelight is allowed to act, low-molecular substances are produced by anoxidation reaction in which light participates, and the low-molecularsubstances are lost due to extraction or vaporization to produce finewaviness similarly. Where oxygen is made to act, low-molecularsubstances are produced by an oxidation reaction, which similarlyresults in fine waviness. Combination of the first and the second stepsproduces both fine pits and waviness that would have developed inoutdoor exposure to accelerate deterioration, whereby outdoordeterioration can be reproduced.

[0044] The language “making active oxygen and light simultaneously acton a test piece” as used herein means that irradiation may not benecessarily made to act on a test piece simultaneously with a treatmentusing an oxidizing agent, provided that light is made to act on the testpiece in the presence of the active oxygen.

[0045] The language “successive and/or alternate steps” as used hereinmeans that the first step, taken as step A, and the second step, takenas step B, can be combined in the order of A-B, B-A, A-B-A-B . . . ,A-B1-B2-A-B1-B2 . . . , and the like, wherein B1 and B2 are differenttreatments included in step B as hereinafter described in detail. Inwhat follows, the first and the second steps will sometimes be referredto as step A and step B, respectively.

[0046] Step A is a step of making active oxygen and light simultaneouslyact on a test piece to accelerate and reproduce the deteriorating actioncausing fine pits, which is one of the deteriorating actions in whichlight takes part. In order to make active oxygen to act, an oxidizingagent is used as an active oxygen-releasing substance. The oxidizingagent to be used is preferably selected from hydrogen peroxide, ozone,peracids, peracid salts, hypohalogenous acids, hypohalogenous acidsalts, and chlorine. Hydrogen peroxide is particularly preferred. Otherknown oxidizing agents are also employable. The oxidizing agent selectedis used in aqueous solution. The oxidizing agent can be allowed to acton a test piece by immersing the test piece in the aqueous solution ofthe oxidizing agent or dropping or spraying the aqueous solution ontothe test piece so that the aqueous solution may run thereon. Step A mayalso be effected in an embodiment wherein the oxidizing agent is made topenetrate into the test piece by the above-described manner and, afterthe aqueous solution is removed by, for example, washing with water, thetest piece is irradiated with light to make the oxidizing agent andlight act simultaneously.

[0047] Where a test piece is, for example, a coated article, thetreatment with active oxygen and light in step A results in developmentof fine pits on the surface of the coating film. This deteriorated stateis chiefly attributed to the oxidation reaction caused by the oxidizingagent and light acting substantially simultaneously. Depending on theoxidizing agent selected, the oxidation reaction causes an oxygenelement to bind to the test piece or causes an element other than oxygento bind to the test piece. In general, the oxidation occurring onorganic materials used outdoors to cause deterioration is a reaction ofoxygen element's binding to the test piece. In order to reproduceoutdoor weathering deterioration, an oxidation reaction in which anoxygen element participates should take place.

[0048] In case where step A is undertaken by using an oxidizing agentwhich involves an oxidation reaction in which an oxygen elementparticipates, it is possible to cause an oxidation reaction with oxygenin step A alone. Where such an oxidizing agent is not chosen, anoxidation reaction with oxygen does not occur in step A. In this case,however, it is possible to induce elements replacement to cause anoxidation reaction with oxygen by properly selecting the treatment to beundertaken in the following step B. In this case step B is required tocomprise a means for allowing at least oxygen to act.

[0049] Step B is to make at least one of water, oxygen, and light to acton the test piece. Step B specifically includes the following treatmentsB1 to B6.

[0050] Treatment B1: immersing a test piece in warm water. Thetemperature of the warm water for the warm water immersion as usedherein is from about 30° C. to about 100° C.

[0051] Treatment B2: immersing a test piece in warm water whileirradiating.

[0052] Treatment B3: the treatment B2 in which the warm water containsdissolved oxygen in equilibrium with an oxygen partial pressure of 0.2atm or more.

[0053] Treatment B4: irradiating a test piece in a gas containing steam.

[0054] Treatment B5: the treatment B4 in which the gas further contains0.2 atm or more of oxygen.

[0055] Treatment B6: a treatment according to a conventional weatheringtest involving water as a load factor. The conventional weathering testuseful in treatment B6 includes an outdoor exposure test, a traced andcollected sunlight exposure test, and an artificial acceleratedweathering test using various artificial light sources.

[0056] Light to be used in steps A and B is not particularly limited aslong as it has energy to activate the material making up the test piece.Because many of industrially important materials mutually react withlight having wavelengths not more than 400 nm, it is desirable for theirradiating light to contain light rays having wavelengths of 400 nm orless. Any light source that has been employed in conventional weatheringtests can be adopted. Suitable light includes not only sunlight butlight from artificial light sources, such as a xenon lamp, a metalhalide lamp, a carbon arc lamp, and a UV fluorescent lamp, and acombination thereof. If necessary, an appropriate optical filter can beused in combination.

[0057] Where step B is performed in an artificial environment, it isdesirable that the test piece be kept at 0 to 120° C. At the testpiece's temperature lower than 0° C., the degree of deteriorationacceleration tends to be insufficient for manifesting the effects of theinvention as expected. At the test piece's temperature higher than 120°C., some chemical reaction that would not take place outdoors tends tooccur, failing to obtain the effects as aimed.

[0058] Where the test piece is, for example, a coated article, thedeterioration accelerated in step B results in development of finewaviness on the surface of the coating film.

[0059] The above-described weathering test according to the secondaspect of the invention is preferably carried out by means of aweathering apparatus comprising a container in which a test piece isput, a means for making active oxygen and light simultaneously act onthe test piece, and a means for making at least one of water, oxygen,and light act on the test piece.

[0060] Where a test piece is irradiated with light through the wall ofthe container in which the test piece is placed, the container should bemade of a light-transmitting material. In using light containing UVrays, a material transmitting UV rays, such as silica glass, ispreferred.

[0061] The means for making active oxygen and light simultaneously acton the test piece includes a means for irradiating the test piece asimmersed in an aqueous solution of the oxidizing agent. It is preferredfor the apparatus to have a function for maintaining the temperatureinside the container constant so that the rate of deterioration may beadjusted. A temperature control unit is an effective means formaintaining the temperature inside the container constant.

[0062] The light source may be either the sun or an artificial lightsource. An artificial light source is preferably incorporated into theapparatus. Any known light sources used in conventional artificialaccelerated weathering tests can be utilized, including a xenon lamp, ametal halide lamp, and a UV fluorescent lamp. To control the spectraldistribution of the light from these light sources, it is advantageousto provide an appropriate optical filter between the light source andthe test piece.

[0063] The means for making at least one of water, oxygen, and light acton the test piece includes conventional means employed in an outdoorexposure test, a traced and collected sunlight exposure test, and anartificial accelerated weathering test using various artificial lightsources and the same means as used in step A for making an oxidizingagent aqueous solution and light act on a test piece substantiallysimultaneously except that the oxidizing agent aqueous solution isreplaced with pure water, air containing steam, and the like.

[0064] In a preferred embodiment of the apparatus, a test piece is putin a container made of silica glass, and the container is set in athermostat. The wall of one side of the thermostat is made of a plate ofsilica glass or of glass which also functions as an optical filter. Thetest piece is irradiated with light emitted from an artificial lightsource, such as a xenon lamp, a metal halide lamp, and a UV fluorescentlamp, through the glass plate and the wall of the silica glass-madecontainer.

[0065] The silica glass-made container has an opening at its bottom, theopening connected through piping to an external apparatus from whichliquid or gas is introduced into the container in accordance withprogrammed timing. The substance introduced into the container throughthis opening and piping includes an aqueous solution of hydrogenperoxide in step A and pure water, air at controlled temperature andhumidity, and a special mixed gas having an oxygen partial pressureincreased over that of air in step B. The test is carried outautomatically according to programmed timing.

[0066] The present invention will now be illustrated in greater detailwith reference to Examples in view of Comparative Examples, but itshould be understood that the invention is not construed as beinglimited thereto. In Examples and Comparative Examples, aqueous hydrogenperoxide was used in a prescribed concentration as diluted a 30 wt %reagent of aqueous hydrogen peroxide (available from Wako Pure Chemical)with ion-exchanged water.

EXAMPLE 1

[0067] A steel plate (7 cm×15 cm×0.8 mm) was subjected toelectrodeposition, and a primer and a topcoat of white paint wereapplied to prepare a coated plate as a test piece. Sodium hypochloritehexahydrate (produced by Wako Pure Chemical Industries, Ltd.), which isa liquid substance, was uniformly applied to the coated side of theplate in an amount of 0.5 g/side. The plate was set to stand still in athermostat kept at 40° C. and irradiated with light from a UVfluorescent lamp about 60 mm away from the plate for 10 hours. Anoptical filter was placed between the coated plate and the light sourceso that the light reaching the coated plate might have wavelengths of295 to 400 nm.

[0068] After the irradiation, the coated plate was washed with water anddried, and gloss at 60° was measured with a gloss meter GM-3D(manufactured by Murakami Color Research Laboratory). The 60° gloss ofthe plate immediately after the preparation was 94, whereas that afterthe test was 75.

COMPARATIVE EXAMPLE 1

[0069] A plurality of coated plates prepared in the same manner as inExample 1 were placed in a thermostat set at 40° C. and irradiated withUV light in the same manner as in Example 1 for 1000 hours. Meanwhile,the coated plates were taken out of the thermostat at appropriate timeintervals, washed with water, and dried, and the 60° gloss was measuredin the same manner as in Example 1. As a result, the coated platesshowed no change of gloss from the initial value 94 until the end of the1000-hour irradiation.

EXAMPLE 2

[0070] A plurality of coated plates (3.5 cm×15 cm×0.8 mm) were preparedin the same manner as in Example 1. Each coated plate was put into asilica glass-made cylindrical container (43 mm in diameter; 200 mm inheight, and 2 mm in wall thickness) together with about 150 ml of 3 wt %aqueous hydrogen peroxide, and the container was closed with a siliconerubber stopper. A plurality of the thus prepared containers having thecoated plate and aqueous hydrogen peroxide therein were disposed in athermostat kept at 40° C. in such a manner that the coated side of everyplate might face a UV fluorescent lamp provided outside the thermostatabout 60 mm away from the plate. The coated side of each plate wasirradiated with light from the UV fluorescent lamp under the sameconditions as in Example 1. Meanwhile, the coated plates were taken outof the thermostat at appropriate time intervals, washed with water, anddried, and the 60° gloss was measured in the same manner as inExample 1. The initial 60° gloss immediately after the preparation ofthe test pieces was 94, whereas the 60° gloss after 100-hour irradiationwas 5. The plots of 60° gloss vs. irradiation time (light exposure time)are shown in FIG. 1.

COMPARATIVE EXAMPLE 2

[0071] The same weathering test as in Example 2 was carried on aplurality of coated plates (3.5 cm×15 cm×0.8 mm) prepared in the samemanner as in Example 1, except for replacing the 3 wt % aqueous hydrogenperoxide with ion-exchanged water. As a result, the coated platesunderwent no change of 60° gloss from the initial value 94 until 300hours.

EXAMPLE 3

[0072] A weathering test by irradiation was carried out in the samemanner as in Example 2, except for replacing the 3 wt % aqueous hydrogenperoxide with 1 wt % aqueous solution of sodium peroxocarbonate. Theresults obtained are plotted in FIG. 2.

EXAMPLE 4

[0073] A weathering test using a sunshine weather meter (manufactured bySuga Test Instruments Co., Ltd.) was applied to a plurality of coatedplates prepared in the same manner as in Example 1. The test wasundertaken under standard conditions as specified except that highlypure water to be sprayed to give a water load was replaced with 0.01 wt% aqueous hydrogen peroxide. The coated plate was taken out to measurethe 60° gloss at given time intervals in the same manner as in Example2. The 60° gloss of the coated plate immediately after the preparationwas 94, which decreased to 51 after 500 hours' testing. The plots of 60°gloss vs. testing time are shown in FIG. 3.

COMPARATIVE EXAMPLE 3

[0074] A plurality of coated plates prepared in the same manner as inExample 1 A were subjected to a weathering test using a sunshine weathermeter (manufactured by Suga Test Instruments Co., Ltd.) under standardconditions as specified. The 60° gloss of the coated plates was measuredin the same manner as in Example 4. The initial 60° gloss immediatelyafter the preparation of the coated plate was 94, which decreased to 91after 1000 hours' testing. The 60° gloss plotted against the testingtime is shown in FIG. 4.

EXAMPLE 5

[0075] A coated plate prepared in the same manner as in Example 1 wasimmersed in 30 wt % aqueous hydrogen peroxide (a reagent available fromWako Pure Chemical Industries, Ltd.) at 20° C. for 30 minutes whileshielded from light. The coated plate was taken out of the aqueoushydrogen peroxide and immediately washed with water for 5 seconds. Thewashed coated plate was set in a thermostat at 40° C. and irradiatedwith light from a UV fluorescent lamp placed about 60 mm away from theplate for 10 hours in the same manner as in Example 1. The 60° gloss ofthe coated plate immediately after the preparation was 94, whichdecreased to 88 after the irradiation.

COMPARATIVE EXAMPLE 4

[0076] A coated plate prepared in the same manner as in Example 1 wassubjected to an outdoor exposure test in Okinawa, Japan for 24 months,and the 60° gloss of the coated side was measured every 3 months. The60° gloss immediately after the preparation of the coated plate was 94,which decreased to 67 after 24 months' exposure. The plots of the 60°gloss against the exposure time are shown in FIG. 5.

[0077] Observations:

[0078] Comparison between Example 1 and Comparative Example 1 revealsthat deterioration of a coating film by light can be accelerated bydirectly applying an active oxygen-releasing substance to the coatedplate, whereby reduction in gloss of the coated plate can be reproducedin a shortened period of time. Further, Examples 2 and 3 in view ofComparative Example 2 show that immersion of the test piece in anaqueous solution of an active oxygen-releasing substance achievesreproduction of reduction in gloss in a short time.

[0079] It is seen by comparing Example 4 and Comparative Example 3 thatdeterioration of the coating film of a test piece by light isaccelerated to reproduce reduction in gloss in a short time by sprayingan aqueous solution of an active oxygen-releasing substance to the testpiece. This result applies to conventional artificial acceleratedweathering tests to increase the rate of acceleration of deterioration,thereby enhancing the usefulness of the weathering tests.

[0080] Comparative Example 4 is an outdoor weathering test relying onexposure to natural weathering conditions. The time required for thecoated plate to reduce its 60° gloss to 90 is 12 months in this outdoorweathering, whereas it is 8 hours in Example 2, 12 hours in Example 3,160 hours in Example 4, and 1000 hours in Comparative Example 3.Accordingly, the rate of deterioration in these Examples is 1100, 730,55, and 8.8 times, respectively, that observed in the outdoor weatheringtest. From these rates of accelerated deterioration, it is understoodthat the weathering test according to the first aspect of the inventionachieves remarkable acceleration of deterioration.

APPARATUS EXAMPLE 1

[0081]FIG. 6 illustrates an apparatus by which the first aspect of thepresent invention can be carried out easily. A test piece 15 is immersedin an aqueous solution 12 of an active oxygen-releasing substance andirradiated with UV light emitted from a light source 14 through anoptical filter and the wall of a silica glass-made container 13. Sincethe silica glass container 13 is placed in a thermostat 11, the testpiece 15 is kept at a prescribed temperature.

APPARATUS EXAMPLE 2

[0082] In FIG. 7 is shown another apparatus for suitably carrying outthe weathering test according to the first aspect of the invention. Theapparatus comprises a casing 21, a liquid pan 22, a holding member 23which holds test pieces 25, and a light source 24. The casing 21 has afunction as a thermostat. The liquid pan 22 is put on the bottom of thecasing 21 and contains an aqueous solution of an active oxygen-releasingsubstance. The holding member 23 is positioned in the central portion ofthe casing 21 and is rotatable on a horizontal axis so that a lower partof the holding member 23 may successively be immersed in the aqueoussolution in the pan 22. The holding member 23 is a rotatable cylindricalcage, and the test pieces 25 can be attached to the inner side of thecage with their side to be tested facing the center of the rotation. Thelight source 24 is set in the casing 21 at the center of the rotation ofthe holding member 23 so as to face every test piece 25.

[0083] The holding member 23 revolves on a horizontal axis at a constantspeed by means of a driving mechanism not shown. The speed of revolutionis adjustable in a range of from 1 to 100 revolutions per hour. Thus,each test piece 25 as attached to the holding member 23 revolves in thethermostat at a given speed and, meanwhile, intermittently immersed inthe aqueous solution in the liquid pan 22 and constantly irradiated withlight from the light source 24.

[0084] Each test piece 25 is always irradiated throughout a test cycleconsisting of an immersed state in the aqueous solution, a wet statewith the aqueous solution after emerging from the liquid pan 22, a statein which water is evaporated, and the active oxygen-releasing substanceis concentrated and brought into contact with the surface of each testpiece 25 or penetrating into the inside of the test piece 25, and astate until it is again immersed in the aqueous solution. The test piece25 is repeatedly subjected to this test cycle. As a result,deterioration of each test piece 25 is accelerated efficiently.

EXAMPLE 6

[0085] A coated steel plate prepared in the same manner as in Example 1was subjected to an outdoor exposure test in Aichi, Japan in accordancewith the test method specified in JIS Z2381 except that 0.1 wt % aqueoushydrogen peroxide was sprayed once a day onto the coated surface of theplate under testing at noon for 10 seconds to wet the entire coatedsurface. Part of hydrogen peroxide sprayed penetrates inside the coatingfilm and acts substantially together with light. The test was started inMay and continued for 6 months. After completion of the testing, the 60°gloss of the coated plate was measured in the same manner as in Example1, and the surface profile of the coating film was observed under ascanning electron microscope (SEM) JSM-890 (manufactured by JEOL Ltd.).

[0086] The 60° gloss was 94 immediately after the preparation of thecoated plate and 75 after the 6 months' testing. The SEM observationrevealed fine waviness and fine pits on the surface, which agreed withthe surface profile characteristically observed in outdoordeterioration.

COMPARATIVE EXAMPLE 5

[0087] A plurality of coated plates prepared in the same manner as inExample 1 were subjected to an outdoor exposure test in accordance withthe test method specified in JIS Z2381 concurrently with Example 6. The60° gloss of the coated plate was measured at appropriate timeintervals, and the surface profile of the coating film was observed atthe same time in the same manner as in Example 6.

[0088] The 60° gloss after 6 months exposure showed substantially nochange from the initial value 94. Neither did the SEM observationrevealed any change. When the outdoor exposure test was furthercontinued for an additional 2 years and a half period (3 years intotal), the 60° gloss was reduced to 80, and the surface profile showedfine waviness and fine pits in a mixed state.

EXAMPLE 7

[0089] A plurality coated plates (3.5 cm×15 cm×0.8 mm) prepared in thesame manner as in Example 1 were immersed in warm water at 80° C. for 24hours and then each put into a silica glass-made cylindrical container(43 mm in diameter; 200 mm in height, and 2 mm in wall thickness)together with about 150 ml of 3 wt % aqueous hydrogen peroxide, and eachcontainer was closed with a silicone rubber stopper. The containers wereset upright in a thermostat kept at 40° C. with the coated side of eachcoated plate facing a UV fluorescent lamp which was placed about 60 mmaway from the coated surface, and irradiated with light from the lamp.An optical filter made of glass was placed between the container and thelight source so that the light reaching the coated plate might havewavelengths of 295 to 400 nm.

[0090] During the testing, the coated plates were taken out of thecontainer at appropriate time intervals, and the 60° gloss was measuredin the same manner as in Example 1. After 50 hours' testing, the surfaceprofile of the irradiated coating film was observed. The initial 60°gloss immediately after the preparation of the coated plate was 94,whereas the 60° gloss after 50-hour irradiation was 40. The plots of 60°gloss vs. irradiation time (light exposure time) are shown in FIG. 8.The SEM observation revealed fine waviness and fine pits in a mixedstate on the surface, which agreed with the surface profilecharacteristically observed in outdoor deterioration.

COMPARATIVE EXAMPLE 6

[0091] The same weathering test as in Example 7 was carried on aplurality of coated plates (3.5 cm×15 cm×0.8 mm) prepared in the samemanner as in Example 1, except for replacing the 3 wt % aqueous hydrogenperoxide with ion-exchanged water. The initial 60° gloss immediatelyafter the preparation of the coated plate was 94, whereas that after50-hour irradiation was 89. Under SEM observation, fine waviness wasslightly observed but with no fine pits characteristic of outdoordeterioration.

COMPARATIVE EXAMPLE 7

[0092] The same weathering test as in Example 7 was carried on aplurality of coated plates (3.5 cm×15 cm×0.8 mm) prepared in the samemanner as in Example 1, except that the immersion in 80° C. warm waterwas not conducted. After 50 hours' irradiation, the 60° gloss was 58,and the surface profile under SEM observation displayed fine pitscharacteristic of outdoor deterioration but no fine waviness, anothercharacteristic of outdoor deterioration.

EXAMPLE 8

[0093] A coated plate (3.5 cm×15 cm×0.8 mm) prepared in the same manneras in Example 1 was subjected to 5 cycles of weathering treatments inaccordance with the diagram shown in FIG. 9. Each cycle consisted of:

[0094] treatment 1 in which the coated plate was immersed in deionizedwater in a thermostat set at 60° C. for 6 hours, treatment 2 in whichthe coated plate taken out of the deionized water was put in a silicaglass-made container (43 mm in diameter; 200 mm in height, and 2 mm inwall thickness) together with about 150 ml of 0.5 wt % aqueous hydrogenperoxide, the container closed with a silicone rubber stopper and set ina thermostat at 60° C. a wall of which was made of a glass filter, andthe coated side of the plate irradiated with light from a UV fluorescentlamp for 3 hours through the glass filter and the wall of the silicaglass-made container, and

[0095] treatment 3 in which the aqueous hydrogen peroxide was dischargedfrom the silica glass container, the container was rinsed with deionizedwater, all the deionized water but about 2 ml was discharged, thecontainer was again closed with a silicone rubber stopper, and thecoated plate in the container was irradiated for 15 hours under the sameconditions as in treatment 2.

[0096] Treatment 1 corresponds to a step B, treatment 2 to step A, andtreatment 3 to another step B which is carried out in the same silicaglass container as used in treatment 2 except that the inside of thecontainer was kept in a high humidity atmosphere.

[0097] The 60° gloss of the coating film was measured in the same manneras in Example 1 at every end of one cycle. The surface profile of thecoating film was observed under SEM at the end of 5 cycles. Therelationship between 60° gloss and the number of cycles is shown in FIG.10.

[0098] As is seen from FIG. 10, the 60° gloss, which was 94 immediatelyafter the preparation of the coated plate, was reduced to 30 after 5cycles of treatments. The surface profile after 5 cycles revealed amixed state of fine waviness and fine pits, which was in good agreementwith the conditions characteristic of outdoor deterioration.

EXAMPLE 9

[0099] A sunshine weather meter (Suga Test Instruments Co., Ltd.) wasmodified to have another spray unit in addition to the spray unit forapplying highly pure water. A plurality of coated plates (3.5 cm×15cm×0.8 mm) prepared in the same manner as in Example 1 were set in themodified sunshine weather meter and tested under the standard conditionsas specified for a standard sunshine weather meter, except that loadingwith a spray of highly pure water was preceded by loading with a10-minute spray of 0.01 wt % aqueous hydrogen peroxide from theadditional spray unit along with irradiation. The coated plates weretaken out at given time intervals to measure the 60° gloss in the samemanner as in Example 1. Further, the surface profile of the coating filmafter 500-hour testing was observed in the same manner as in Example 6.The plots of 60° gloss against the testing time are depicted in FIG. 11.

[0100] As can be seen from FIG. 11, the 60° gloss, which was initially94, reduced to 52 after 500-hour testing. The SEM observation revealed amixed state of fine waviness and fine pits on the surface, which agreedwith the state characteristic of outdoor deterioration.

COMPARATIVE EXAMPLE 8

[0101] A plurality of coated plates (3.5 cm×15 cm×0.8 mm) prepared inthe same manner as in Example 1 were tested in the same sunshine weathermeter (unmodified) as used in Example 9 for 1200 hours under thestandard conditions as specified. The coated plates were taken out atgiven time intervals to measure the 60° gloss, and the surface profileof the coating film after 1200-hour testing was observed in the samemanner as in Example 6. The plots of 60° gloss against the testing timeare depicted in FIG. 12.

[0102] As is shown in FIG. 12, the 60° gloss, which was initially 94,reduced to 90 after 1200-hour testing. The SEM observation revealedslight fine waviness but no fine pits which are characteristic ofoutdoor deterioration.

EXAMPLE 10

[0103] A coated plate (3.5 cm×15 cm×0.8 mm) prepared in the same manneras in Example 1 was subjected to the same weathering test as in Example6, except for replacing the aqueous hydrogen peroxide with a 0.25 wt %aqueous solution of chlorine. As a result, the 60° gloss, which wasinitially 94, reduced to 85 after the 6-month testing. The surfaceprofile under SEM had fine waviness and fine pits and agreed with thatobserved characteristically in outdoor deterioration.

[0104] Observations:

[0105] Comparative Example 5 consists of only step B of the twoessential steps involved in the second aspect of the invention. Example6 is a combination of the step B of Comparative Example 5 and step A inwhich the surface of the coated plate is wetted with aqueous hydrogenperoxide. Obviously, deterioration by outdoor exposure is accelerated inExample 6.

[0106] Comparative Example 6 is the same as in Example 7 except forreplacing UV irradiation in aqueous hydrogen peroxide (step A in Example7) with UV irradiation in pure water (corresponding to step B in Example7). That is, Comparative Example 6 practically consists of only step B.On the other hand, Comparative Example 7 presents omission of theimmersion in warm water from Example 7 and consists of only step A. Nofine pits characteristic of outdoor deterioration was observed inComparative Example 6 (only step B), and no fine waviness alsocharacteristic of outdoor deterioration was observed in ComparativeExample 7 (only step A). To the contrary, the coated plate tested inExample 7 revealed both fine pits and fine waviness, demonstratinghighly accurate reproduction of outdoor deterioration.

[0107] Example 8 shows testing equipment and procedures for efficientlyreproducing the aging of a material attending outdoor exposure byrepetition of a combination of step A and step B.

[0108] In Example 9 is demonstrated an embodiment in which an availableaccelerated weathering apparatus was slightly modified so as to servefor the weathering test according to the second aspect of the inventionthereby to produce the effects as intended. In this modified apparatus,aqueous hydrogen peroxide is sprayed to the coated plate whileirradiated to embody step A, and the situation with no spray of aqueoushydrogen peroxide corresponds to step B. By use of the modifiedapparatus steps A and B can be performed successively and/oralternately. Compared with Comparative Example 8, it is obvious thatExample 9 achieves the effects as intended in the invention.

[0109] Example 10 displays use of an oxidizing agent causing an elementother than oxygen to act in step A. On comparing with the results ofComparative Example 5, it is apparent that the effects as aimed in theinvention can be accomplished with such an oxidizing agent as well.

[0110] While the invention has been described in detail and withreference to specific examples thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

What is claimed is:
 1. A weathering test method comprising making active oxygen and light simultaneously act on a test piece.
 2. A weathering test method according to claim 1, wherein said active oxygen is of an oxidizing agent.
 3. A weathering test method according to claim 2, wherein said oxidizing agent is at least one member selected from the group consisting of hydrogen peroxide, ozone, peracids, peracid salts, hypohalogenous acids, and hypohalogenous acid salts.
 4. A weathering test method according to claim 1, wherein said light has a wavelength of 400 nm or less.
 5. A weathering test method according to claim 1, wherein said active oxygen is of aqueous hydrogen peroxide having a concentration of 0.01 to 10% by weight.
 6. A weathering test method according to claim 1, wherein said light is made to act on the test piece in the presence of the active oxygen.
 7. A weathering apparatus comprising a container in which a test piece is put, a means for making active oxygen act on the test piece, and a means for making light act on the test piece.
 8. A weathering apparatus according to claim 7, wherein said means for making light act is at least one of a xenon lamp, a metal halide lamp, a carbon arc lamp, an ultraviolet fluorescent lamp, and sunlight.
 9. A weathering apparatus according to claim 7, wherein said test piece is a coated plate, said container is a silica glass container containing an aqueous solution of a substance capable of releasing active oxygen, said container is set upright in a closed state in a thermostat with the coated side of said coated plate facing a light source, and an optical filter is provided between said light source and said container.
 10. A weathering apparatus according to claim 7, which comprises a casing having a function as a thermostat, a liquid pan which is put on the bottom of the casing and contains an aqueous solution of a substance capable of releasing active oxygen, a test piece holding member, and a light source; said test piece holding member is a cylinder positioned in the central portion of the casing and is rotatable on a horizontal axis so that the lower part thereof may successively be immersed in the aqueous solution in the liquid pan, and said light source being set in the casing at the center of the rotation of the test piece holding member so as to face every test piece attached to the inner side of the holding member.
 11. A weathering test method comprising successive and/or alternate steps of making active oxygen and light simultaneously act on a test piece and making at least one of light, oxygen, and water to act on the test piece.
 12. A weathering test method according to claim 11, wherein said active oxygen is of an oxidizing agent.
 13. A weathering test method according to claim 12, wherein said oxidizing agent is at least one member selected from the group consisting of hydrogen peroxide, ozone, peracids, peracid salts, hypohalogenous acids, hypohalogenous acid salts, and chlorine.
 14. A weathering test method according to claim 11, wherein said step of making at least one of light, oxygen, and water to act is performed by immersing the test piece in warm water.
 15. A weathering test method according to claim 11, wherein said step of making at least one of light, oxygen, and water to act is performed by irradiating the test piece with light in a gas containing steam and oxygen.
 16. A weathering test method according to claim 11, wherein said light is made to act on the test piece in the presence of the active oxygen.
 17. A weathering apparatus comprising a container in which a test piece is put, a means for making active oxygen and light simultaneously act on the test piece, and a means for making at least one of water, oxygen, and light act on the test piece.
 18. A weathering apparatus according to claim 17, wherein said means for making at least one of water, oxygen, and light act is at least one of a xenon lamp, a metal halide lamp, a carbon lamp, an ultraviolet fluorescent lamp, and sunlight.
 19. A weathering apparatus according to claim 17, wherein said test piece is a coated plate, said container is a silica glass container and is set upright in a closed state in a thermostat with the coated side of said coated plate facing a light source, and an optical filter is provided between said light source and said container. 